The present invention relates to a library system which stores a plurality of data cartridges, such as a magnetic tape, magnetic disk, optical disk and magneto-optical disk, selectively takes up a desired data cartridge from these data cartridges, and can perform a data storage medium (i.e., data cartridge) transfer between a library device which performs data reading/writing and a library device stacked in layers in this library system by use of an internal drive unit.
A conventional library system which stores data cartridges in multiple cells of a magazine, selectively takes up a desired data cartridge from these data cartridges, and performs data reading/writing by use of a drive unit (which may be called a data storage system).
When a data cartridge within such a conventional library device is to be moved to another library device of the same configuration, such movement has been manually carried out.
Thus, manpower has been dedicated to a library device for a time or at given time intervals, and this has required labor costs. Furthermore, it has been necessary to stop a library device when a user takes out cartridges from the library system or loads them into the library device, and thus the efficiency of the library system decreases.
Also, in the case of a library system in which library devices are merely stacked in layers, there has been no mechanism for data cartridges to move between the library devices. Thus, even when a library device has an empty drive, a data cartridge housed in another drive unit cannot use the empty drive, and thus the working rate of the whole library system is low.
Therefore, a library device has been proposed in which an area in which an elevator ascends and descends is newly provided in the space of a magazine and a drive unit is arranged along a transfer area of a cartridge access device. When this library device is vertically stacked in multiple layers, elevator areas of the library devices stacked in layers become connected to each another in a line, thereby allowing each data cartridge to move between libraries above and below the data cartridge, and making it possible to solve various problems as described above.